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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      div {
        width: 100px;
        height: 100px;
        border: 1px solid #000;
      }
    </style>
  </head>
  <body>
    <div></div>
    <script>
      var div = document.querySelector("div");

      // 定时器
      setTimeout(function () {
        div.style.display = "none";
      }, 5000);
    </script>
  </body>
</html>
